Valves having a magnetic drive, referred to as solenoid valves below, use a core movable along an axial direction which can be shifted between a first and a second end position through electromagnetic interaction with the magnetic field of one or more coil(s). In a solenoid valve, the control of the flow is realized via the travel of the core moved with respect to the coil or coils, the flow being directly connected to the position of the core or to the core travel. When the core travel does not change or is even reduced although an appropriate voltage is applied, a malfunction of the solenoid valve is to be assumed which can be caused, e.g., by a blocked core. Within the context of condition monitoring, it is desired to detect such error conditions.
The position of the core of a solenoid valve could be detected using an additional sensor which would however have to be integrated in the solenoid valve. This sensor could provide an appropriate measured value for the condition monitoring. However, an additional sensor means extra charges and possibly higher constructional expenditure for the solenoid valve.
Alternative approaches use the properties of the coil or coils of a solenoid valve and detect, for example, a current drop directly after pick-up of the solenoid valve. Though a solution of this type can do without additional sensors, a disadvantage consists in that a core movement must always take place to obtain appropriate measured values for the condition monitoring. In the running operation of a solenoid valve, the core movements are however limited to planned switching operations. As a result, the condition monitoring in the running operation would be limited to individual points in time, more specifically to the switching operations. Therefore, a continuous condition monitoring independent of the switching operations cannot be realized.